Use of shared feedback among two or more reactive schemes

ABSTRACT

A power delivery system may include a power converter configured to electrically couple to a power source and further configured to supply electrical energy to one or more loads electrically coupled to an output of the power converter and control circuitry configured to control the power converter in accordance with a control variable. The control circuitry may include a first control mechanism configured to generate a first intermediate control variable based on a first physical quantity associated with the power delivery system, a second control mechanism configured to generate a second intermediate control variable based on a second physical quantity associated with the power delivery system, a selector configured to select the control variable from the first intermediate control variable and the second intermediate control variable, and a shared feedback memory element configured to feed back the control variable to inputs of the first control mechanism and the second control mechanism, such that the first control mechanism generates the first intermediate control variable based on the first physical quantity and the control variable, and the second control mechanism generates the second intermediate control variable based on the second physical quantity and the control variable.

RELATED APPLICATION

The present disclosure claims priority to U.S. Provisional PatentApplication Ser. No. 63/058,032, filed Jul. 29, 2020, which isincorporated by reference herein in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates in general to circuits for electronicdevices, including without limitation personal portable devices such aswireless telephones and media players, and more specifically, tolimiting current in a power converter.

BACKGROUND

Portable electronic devices, including wireless telephones, such asmobile/cellular telephones, tablets, cordless telephones, mp3 players,and other consumer devices, are in widespread use. Such a portableelectronic device may include circuitry for implementing a powerconverter for converting a battery voltage (e.g., provided by alithium-ion battery) into a supply voltage delivered to one or morecomponents of the portable electronic device. The power delivery networkmay also regulate such supply voltage, and isolate the downstream loadsof these one or more devices from fluctuation in an output voltage ofthe battery over the course of operation.

In addition to regulating the supply rail for the supply voltage, it maybe desirable for the power converter (or a control circuit for the powerconverter) to provide for active protection mechanisms to limit anamount of current that can be drawn by the one or more componentspowered from the supply rail.

SUMMARY

In accordance with the teachings of the present disclosure, one or moredisadvantages and problems associated with existing approaches tooperating a power converter may be reduced or eliminated.

In accordance with embodiments of the present disclosure, a powerdelivery system may include a power converter configured to electricallycouple to a power source and further configured to supply electricalenergy to one or more loads electrically coupled to an output of thepower converter and control circuitry configured to control the powerconverter in accordance with a control variable. The control circuitrymay include a first control mechanism configured to generate a firstintermediate control variable based on a first physical quantityassociated with the power delivery system, a second control mechanismconfigured to generate a second intermediate control variable based on asecond physical quantity associated with the power delivery system, aselector configured to select the control variable from the firstintermediate control variable and the second intermediate controlvariable, and a shared feedback memory element configured to feed backthe control variable to inputs of the first control mechanism and thesecond control mechanism, such that the first control mechanismgenerates the first intermediate control variable based on the firstphysical quantity and the control variable, and the second controlmechanism generates the second intermediate control variable based onthe second physical quantity and the control variable.

In accordance with these and other embodiments of the presentdisclosure, a method may be used in a power delivery system having apower converter configured to electrically couple to a power source andfurther configured to supply electrical energy to one or more loadselectrically coupled to an output of the power converter. The method mayinclude generating, with a first control mechanism, a first intermediatecontrol variable based on a first physical quantity associated with thepower delivery system. The method may further include generating, with asecond control mechanism, a second intermediate control variable basedon a second physical quantity associated with the power delivery system.The method may also include selecting a control variable from the firstintermediate control variable and the second intermediate controlvariable, controlling the power converter in accordance with a controlvariable, storing the control variable in a shared feedback memoryelement, and feeding back the control variable to inputs of the firstcontrol mechanism and the second control mechanism, such that the firstcontrol mechanism generates the first intermediate control variablebased on the first physical quantity and the control variable, and thesecond control mechanism generates the second intermediate controlvariable based on the second physical quantity and the control variable.

In accordance with these and other embodiments of the presentdisclosure, a mobile device may include a power source, one or moreloads, a power converter electrically coupled to the power source andfurther configured to supply electrical energy to the one or more loads,and control circuitry configured to control the power converter inaccordance with a control variable. The control circuitry may include afirst control mechanism configured to generate a first intermediatecontrol variable based on a first physical quantity associated with thepower delivery system, a second control mechanism configured to generatea second intermediate control variable based on a second physicalquantity associated with the power delivery system, a selectorconfigured to select the control variable from the first intermediatecontrol variable and the second intermediate control variable, and ashared feedback memory element configured to feed back the controlvariable to inputs of the first control mechanism and the second controlmechanism, such that the first control mechanism generates the firstintermediate control variable based on the first physical quantity andthe control variable, and the second control mechanism generates thesecond intermediate control variable based on the second physicalquantity and the control variable.

Technical advantages of the present disclosure may be readily apparentto one skilled in the art from the figures, description and claimsincluded herein. The objects and advantages of the embodiments will berealized and achieved at least by the elements, features, andcombinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates a block diagram of selected components of an examplepower delivery network, in accordance with embodiments of the presentdisclosure;

FIG. 2 illustrates an example graph of an open circuit voltage of abattery versus the battery's state of charge, in accordance withembodiments of the present disclosure;

FIG. 3 illustrates a block diagram of selected components of an exampleequivalent circuit model for a battery, in accordance with embodimentsof the present disclosure;

FIG. 4 illustrates an example graph of a battery voltage and a batterycurrent versus time associated with a current step drawn from a battery,in accordance with embodiments of the present disclosure;

FIG. 5 illustrates an example first-order model of a battery simplifiedto a time-varying voltage source in series with an equivalent seriesresistance, in accordance with embodiments of the present disclosure;

FIG. 6 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for battery protection, inaccordance with embodiments of the present disclosure;

FIG. 7 illustrates a block diagram of selected impedances within thepower delivery network shown in FIG. 1, in accordance with embodimentsof the present disclosure;

FIG. 8 illustrates an example graph of an output power of a powerconverter versus battery current drawn by the power converter, inaccordance with embodiments of the present disclosure;

FIG. 9 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for power converter stability, inaccordance with embodiments of the present disclosure;

FIG. 10 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for power limit considerations, inaccordance with embodiments of the present disclosure;

FIG. 11 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for current limit considerations,in accordance with embodiments of the present disclosure; and

FIG. 12 illustrates a block diagram of selected components of examplecontrol circuitry for controlling a power converter, in accordance withembodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a block diagram of selected components of an examplepower delivery network 10, in accordance with embodiments of the presentdisclosure. In some embodiments, power delivery network 10 may beimplemented within a portable electronic device, such as a smart phone,tablet, game controller, and/or other suitable device.

As shown in FIG. 1, power delivery network 10 may include a battery 12and a power converter 20 configured to convert a battery voltageV_(CELL) generated by battery 12 into a supply voltage V_(SUPPLY) usedto power a plurality of downstream components 18, wherein eachdownstream component 18 may draw a respective current I_(LOAD1),I_(LOAD2), I_(LOAD3), etc., from the output of power converter 20,meaning an aggregate load current I_(LOAD)=I_(LOAD1)+I_(LOAD2)+ . . .+I_(LOADN) may be generated by power converter 20. Power converter 20may be implemented using a boost converter, buck converter, buck-boostconverter, transformer, charge pump, and/or any other suitable powerconverter. Downstream components 18 of power delivery network 10 mayinclude any suitable functional circuits or devices of power deliverynetwork 10, including without limitation other power converters,processors, audio coder/decoders, amplifiers, display devices, etc.

As shown in FIG. 1, power delivery network 10 may also include controlcircuitry 30 for controlling operation of power converter 20, includingswitching and commutation of switches internal to power converter 20. Inaddition, as described in greater detail below, control circuitry 30 mayalso implement active protection mechanisms for limiting currentI_(CELL) drawn from battery 12.

Lithium-ion batteries are typically known to operate from 4.2 V down to3.0 V, known as an open circuit voltage V_(OC) of the battery (e.g.,battery 12). As a battery discharges due to a current drawn from thebattery, the state of charge of the battery may also decrease, and opencircuit voltage V_(OC) (which may be a function of state of charge) mayalso decrease as a result of electrochemical reactions taking placewithin the battery, as shown in FIG. 2. Outside the range of 3.0 V and4.2 V for open circuit voltage V_(OC), the capacity, life, and safety ofa lithium-ion battery may degrade. For example, at approximately 3.0 V,approximately 95% of the energy in a lithium-ion cell may be spent(i.e., state of charge is 5%), and open circuit voltage V_(OC) would beliable to drop rapidly if further discharge were to continue. Belowapproximately 2.4V, metal plates of a lithium-ion battery may erode,which may cause higher internal impedance for the battery, lowercapacity, and potential short circuit. Thus, to protect a battery (e.g.,battery 12) from over-discharging, many portable electronic devices mayprevent operation below a predetermined end-of-discharge voltageV_(CELL-MIN).

FIG. 3 illustrates a block diagram of selected components of anequivalent circuit model for battery 12, in accordance with embodimentsof the present disclosure. As shown in FIG. 3, battery 12 may be modeledas having a battery cell 32 having an open circuit voltage V_(OC) inseries with a plurality of parallel resistive-capacitive sections 34 andfurther in series with an equivalent series resistance 36 of battery 12,such equivalent series resistance 36 having a resistance of R₀.Resistances R₁, R₂, . . . R_(N), and respective capacitances C₁, C₂, . .. , C_(N) may model battery chemistry-dependent time constants τ₁, τ₂, .. . , τ_(N), that may be lumped with open circuit voltage V_(OC) andequivalent series resistance 36. Notably, an electrical node depictedwith voltage V_(CELL-EFF) in FIG. 3 captures the time varying dischargebehavior of battery 12, and battery voltage V_(CELL) is an actualvoltage seen at the output terminals of battery 12. Voltage V_(CELL-EFF)may not be directly measurable, and thus battery voltage V_(CELL) may bethe only voltage associated with battery 12 that may be measured toevaluate battery state of health. Also of note, at a current draw ofzero (e.g., I_(CELL)=0), battery voltage V_(CELL) may be equal tovoltage V_(CELL-EFF) which may in turn be equal to an open circuitvoltage V_(OC) at a given state of charge.

FIG. 4 illustrates example graphs of battery voltage V_(CELL) andbattery current I_(CELL) versus time associated with a current stepdrawn from battery 12, in accordance with embodiments of the presentdisclosure. As shown in FIG. 4, in response to a current step event,battery voltage V_(CELL) may respond to the step, as the response curvefor battery voltage V_(CELL) experiences an initial instantaneous drop(e.g., due to equivalent series resistance 36) and time-dependentvoltage drops due to time constants τ₁, τ₂, . . . , τ_(N). Open circuitvoltage V_(OC) and the various impedances R₀, R₁, R₂, . . . R_(N), maybe a function of state of charge of battery 12, thus implying that atransient response to a new, fully-charged battery could besignificantly different from that of an aged, partially-dischargedbattery.

In operation, control circuitry 30 may determine a maximum batterycurrent I_(CELL) that may be drawn from battery 12 at any given instantbased on one or more constraints, including protection of battery 12,stability of power converter 20, and/or limitations associated withpractical limitations.

A first constraint that may be imposed by control circuitry 30 isbattery-imposed limitations for the maximum of battery current I_(CELL).To illustrate application of this constraint, FIG. 5 illustrates afirst-order model of battery 12 simplified to a time-varying voltagesource 38 with voltage V_(CELL-EFF) in series with equivalent seriesresistance 36 having a resistance value of R₀, in accordance withembodiments of the present disclosure. A maximum battery currentI_(CELL-MAX) that battery 12 may be capable of delivering may bedirectly dependent on equivalent series resistance 36. Battery currentI_(CELL) must pass through equivalent series resistance 36, which mayreduce battery voltage V_(CELL) from voltage V_(CELL-EFF) by an amountequal to resistance R₀ multiplied by battery current I_(CELL) (e.g.,V_(CELL)=V_(CELL-EFF)−R₀I_(CELL)). Perhaps more significantly, batterycurrent I_(CELL) flowing through equivalent series resistance 36 maycause power dissipation within battery 12 that is equal to resistance R₀multiplied by the square of battery current I_(CELL) (e.g., P=R₀I_(CELL)²). At high rates of discharge, battery current I_(CELL) may lead tosignificant heating within battery 12. The requirement discussed abovethat battery voltage V_(CELL) must remain above end-of-discharge voltageV_(CELL-MIN) sets a limitation on maximum battery current I_(CELL-MAX),as given by:

$I_{C{ELL}\text{-}{MAX}} = \frac{V_{C{ELL}\text{-}EFF} - V_{{CELL}\text{-}{MIN}}}{R_{0}}$

Accordingly, maximum battery current I_(CELL-MAX) may be a function ofvoltage V_(CELL-EFF), assuming only battery-imposed limitations, and maybe plotted as illustrated by line CON1 shown in FIG. 6.

To enforce such limitation, control circuitry 30 may implement an activeprotection scheme to ensure that end-of-discharge voltage V_(CELL-MIN)is not violated, despite transient loads on power converter 20, so as toavoid damage to battery 12. For example, control circuitry 30 may beconfigured to monitor battery voltage V_(CELL) at terminals of battery12 and vary maximum battery current I_(CELL-MAX) drawn by powerconverter 20 as shown by constraint CON1 in FIG. 6 in order to ensurebattery 12 is not over-discharged to pushed beyond its safe operatingrange, in order to extend life of battery 12. However, complicating suchcontrol of maximum battery current I_(CELL-MAX) is that the transientresponse of battery 12 may be a function of multiple time constants(e.g., τ₁, τ₂, . . . , τ_(N)) as described above, and it may beunfeasible or uneconomical to measure such time constants for a givenbattery and vary maximum battery current I_(CELL-MAX) in a feedforwardmanner Thus, as further described below, control circuitry 30 mayimplement a negative feedback control loop around power converter 20that may monitor battery voltage V_(CELL) and vary maximum batterycurrent I_(CELL-MAX) to maintain battery voltage V_(CELL) at a desiredtarget value.

In addition to limiting current to provide for protection of battery 12as described above, it may also be desirable to limit current to providestability for power converter 20, in order to operate beyond a maximumpower point into a region of instability of power converter 20, asdescribed in greater detail below. To illustrate, reference is made toFIG. 7, which depicts a detailed block diagram of selected impedanceswithin power delivery network 10 shown in FIG. 1, in accordance withembodiments of the present disclosure. As shown in FIG. 7, powerdelivery network 10 may be modeled with battery 12 as shown in FIG. 5 inseries with a trace resistor 52, a current sense resistor 54, animpedance 56 to model equivalent losses in power converter 20, and aload 58 representing the aggregate of downstream devices 18. Traceresistor 52 may have a resistance R_(TRACE) representing a resistance ofelectrical conduit between battery 12 and power converter 20 (e.g., aconnector, printed circuit board trace, etc.). Sense resistor 54 mayhave a resistance R_(SNS) and may be used to sense battery currentI_(CELL) based on a voltage drop across sense resistor 54 (e.g., thedifference between sense voltage V_(SNS) and battery voltage V_(CELL))and resistance R_(SNS) in accordance with Ohm's law. Impedance 56 maymodel losses inside power converter 20 with resistance R_(LOSS). Afteraccounting for power losses occurring in these various impedances, powerconverter 20 may deliver output power P_(OUT) to load 58, given as:

P _(OUT) =I _(CELL) V _(CELL-EFF) −I _(CELL) ² R _(TOT)

where

R _(TOT) =R ₀ +R _(TRACE) +R _(SNS) +R _(LOSS)

For a given total resistance R_(TOT) and given voltage V_(CELL-EFF),there may exist a maximum power P_(MAX) for output power P_(OUT) ofpower delivery network 10 as a function of battery current I_(CELL) thatoccurs at a current I_(PMAX), as shown in FIG. 8, where current I_(PMAX)may be given by:

$I_{P{MAX}} = \frac{V_{{CELL}\text{-}EFF}}{2R_{TOT}}$

Thus, it is shown from FIG. 8 that power delivery system 10 will operatewith optimum power efficiency and stability if I_(CELL)<I_(PMAX), andwill operate in a region of instability (negative slope of output powerP_(OUT) versus battery current I_(CELL)) when I_(CELL)>I_(PMAX). Thismaximum allowable current I_(PMAX) may be plotted as shown in FIG. 9 asconstraint CON2 superimposed over constraint CON1 for maximum batterycurrent I_(CELL-MAX) depicted in FIG. 6. Because total resistanceR_(TOT) is greater than equivalent series resistance R₀, it may beevident that the slope of constraint CON1 is steeper than the slope ofconstraint CON2. On extrapolation, the line of constraint CON2 mayintercept the horizontal axis of voltage V_(CELL-EFF) at 0 V, which isnot shown in FIG. 9, as many batteries (e.g., lithium-ion batteries)will not be allowed to drop to such magnitude.

For high-efficiency power converters, impedance 56 may be negligiblecompared to equivalent series resistance 36, trace resistor 52, andsense resistor 54, such that total resistance R_(TOT) may be rewrittenas:

R _(TOT) ≈R ₀ +R _(TRACE) +R _(SNS)

As battery 12 is discharged with use, equivalent series resistance 36may increase and voltage V_(CELL-EFF) may decrease accordingly.Therefore, maximum allowable current I_(PMAX) corresponding to maximumpower P_(MAX) may be a function of voltage V_(CELL-EFF) and impedancesof power delivery network 10.

In addition to limiting current to provide for protection of battery 12as described above, and in addition to limiting current to providestability for power converter 20 as described above, it may also oralternatively be desirable to limit current based on considerations ofpractical implementations, as described in greater detail below.

As an example, beyond a certain voltage V_(CELL-EFF), the maximumbattery current I_(CELL), and therefore the maximum power deliverycapability P_(MAX), of power converter 20 may become so large that thedesign of power converter 20 becomes increasingly difficult or evenunfeasible. Practical limitations such as, for example, inductorsaturation current and required dynamic range of current sensingcircuitry in power converter 20 may dictate an upper power limit P_(LIM)be placed on output power P_(OUT). Thermal considerations may also needto be taken into consideration and may drive a need to limit maximumpower delivery from power converter 20.

Assuming output power P_(OUT) is limited to power limit P_(LIM), a powerbalance equation for power delivery system 10 may be written as:

I _(CELL) ² R _(TOT) −I _(CELL) V _(CELL-EFF) +P _(LIM)=0

which can be rewritten as:

$I_{{CELL}\text{-}{LIM}} = {I_{P{MAX}} - \sqrt{\frac{P_{MAX} - P_{LIM}}{R_{TOT}}}}$

This maximum allowable current I_(CELL-LIM) may be plotted as shown inFIG. 10 as constraint CON3A superimposed over constraints CON1 and CON2depicted in FIG. 9. A separation between two power limited regions forP_(MAX) and P_(LIM) are graphically shown in FIG. 10 as occurring at abreakpoint between the curves representing constraints CON2 and CON3A.In the region limited by power limit P_(LIM), a maximum for batterycurrent I_(CELL) may be set by the lower of the two values for maximumallowable current. As is shown in FIG. 10, along the curve forconstraint CON3A, the maximum current for battery current I_(CELL) mayincrease as voltage V_(CELL-EFF) decreases.

In addition to limiting current to provide for protection of battery 12as described above, limiting current to provide stability for powerconverter 20 as described above, and limiting current for power limitingconsiderations, it may also or alternatively be desirable to apply afixed current limit I_(FIXED) based on considerations of practicalimplementations, as described in greater detail below. This maximumallowable current I_(FIXED) may be plotted as shown in FIG. 11 asconstraint CON3B superimposed over constraints CON1, CON2, and CON3Adepicted in FIG. 10. Thus the maximum current for battery currentI_(CELL) may be set by the lowest of the four values for maximumallowable current.

FIG. 12 illustrates a block diagram of selected components of examplecontrol circuitry 30 for controlling power converter 20, in accordancewith embodiments of the present disclosure. In operation, controlcircuitry 30 may implement the current-limiting scheme described above.As shown in FIG. 12, control circuitry 30 may include reactive engines60, 62, and 64 configured to apply constraints C1, C2, and C3A,respectively, to generate maximum constraint currents I_(MAX1),I_(MAX2), and I_(MAX3), respectively. A minimum block 66 may select theminimum of maximum allowable current I_(FIXED) (corresponding toconstraint C3B) and maximum constraint currents I_(MAX1), I_(MAX2), andI_(MAX3) to generate maximum battery current I_(CELL-MAX). Controlcircuitry 30 may also include a current controller 68 that may, based onsupply voltage V_(SUPPLY) and maximum battery current I_(CELL-MAX),generate switch control signals to power converter 20 to control anamount of current drawn by power converter 20.

As shown in FIG. 12, reactive engine 60 may apply constraint C1 based onbattery voltage V_(CELL) and the value of maximum battery currentI_(CELL-MAX) feedback from minimum block 66. Similarly, each of reactiveengines 62 and 64 may apply constraints C2 and C3A based on sensevoltage V_(SNS) and the value of maximum battery current I_(CELL-MAX)feedback from minimum block 66. Accordingly, each reactive engine 60,62, and 64 may be an independent mechanism to limit power transfer ofpower converter 20 to satisfy two or more independent constraints (e.g.,constraints C1, C2, and C3A) while each reactive engine 60, 62, and 64is updated, from common memory element 69, with the common controlparameter (e.g., maximum battery current I_(CELL-MAX)) that eachreactive engine 60, 62, and 64 controls.

In operation, based on the previous sampled values for maximum batterycurrent I_(CELL-MAX) stored in common memory element 69 and therespective input for a reactive engine 60, 62, and 64 (e.g., batteryvoltage V_(CELL) or sense voltage V_(SNS)), a reactive engine 60, 62,and 64 may increment or decrement (or, in some embodiments, leaveunchanged) its respective maximum constraint current I_(MAX1), I_(MAX2),and I_(MAX3). It is possible in some scenarios that when one of reactiveengines 60, 62, and 64 increments its respective maximum constraintcurrent, another of reactive engines 60, 62, and 64 may decrement itsrespective maximum constraint current. However, at any given time, nomore than one of reactive engines 60, 62, and 64 may set the final statevariable of maximum battery current I_(CELL-MAX).

At the instant one of reactive engines 60, 62, and 64 becomes thedominant engine (e.g., its respective maximum constraint currentI_(MAX1), I_(MAX2), and I_(MAX3) is lower than maximum allowable currentI_(FIXED) and the other maximum constraint currents), due to the sharedfeedback of the global maximum battery current I_(CELL-MAX), the newdominant engine may begin incrementing or decrementing its respectivemaximum constraint current from the exact value that its predecessordominant engine had generated at such instant. Accordingly, because suchglobal feedback approach may prevent a large instantaneous change inmaximum battery current I_(CELL-MAX), changes in maximum battery currentI_(CELL-MAX) may be unlikely to cause glitches in the current drawn bypower converter 20, thus minimizing or eliminating current and/orvoltage overshoots or undershoots within power delivery network 10.Also, providing for one shared feedback path (and associated circuitry,such as integrators or memory elements) among reactive engines 60, 62,and 64, as opposed to each having their own individual feedback paths(and associated circuitry, such as integrators or memory elements), mayreduce circuit size, complexity, and cost.

As used herein, when two or more elements are referred to as “coupled”to one another, such term indicates that such two or more elements arein electronic communication or mechanical communication, as applicable,whether connected indirectly or directly, with or without interveningelements.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Similarly,where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to the exampleembodiments herein that a person having ordinary skill in the art wouldcomprehend. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, or component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative. Accordingly, modifications, additions, oromissions may be made to the systems, apparatuses, and methods describedherein without departing from the scope of the disclosure. For example,the components of the systems and apparatuses may be integrated orseparated. Moreover, the operations of the systems and apparatusesdisclosed herein may be performed by more, fewer, or other componentsand the methods described may include more, fewer, or other steps.Additionally, steps may be performed in any suitable order. As used inthis document, “each” refers to each member of a set or each member of asubset of a set.

Although exemplary embodiments are illustrated in the figures anddescribed below, the principles of the present disclosure may beimplemented using any number of techniques, whether currently known ornot. The present disclosure should in no way be limited to the exemplaryimplementations and techniques illustrated in the drawings and describedabove.

Unless otherwise specifically noted, articles depicted in the drawingsare not necessarily drawn to scale.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the disclosureand the concepts contributed by the inventor to furthering the art, andare construed as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present disclosurehave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the disclosure.

Although specific advantages have been enumerated above, variousembodiments may include some, none, or all of the enumerated advantages.Additionally, other technical advantages may become readily apparent toone of ordinary skill in the art after review of the foregoing figuresand description.

To aid the Patent Office and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims or claimelements to invoke 35 U.S.C. § 112(f) unless the words “means for” or“step for” are explicitly used in the particular claim.

What is claimed is:
 1. A power delivery system, comprising: a powerconverter configured to electrically couple to a power source andfurther configured to supply electrical energy to one or more loadselectrically coupled to an output of the power converter; and controlcircuitry configured to control the power converter in accordance with acontrol variable, comprising: a first control mechanism configured togenerate a first intermediate control variable based on a first physicalquantity associated with the power delivery system; a second controlmechanism configured to generate a second intermediate control variablebased on a second physical quantity associated with the power deliverysystem; a selector configured to select the control variable from thefirst intermediate control variable and the second intermediate controlvariable; and a shared feedback memory element configured to feed backthe control variable to inputs of the first control mechanism and thesecond control mechanism, such that: the first control mechanismgenerates the first intermediate control variable based on the firstphysical quantity and the control variable; and the second controlmechanism generates the second intermediate control variable based onthe second physical quantity and the control variable.
 2. The powerdelivery system of claim 1, wherein the control variable is a maximumelectrical current associated with the power delivery system.
 3. Thepower delivery system of claim 2, wherein: the first intermediatecontrol variable is a first electrical current variable; the secondintermediate control variable is a second electrical current variable;and the selector is configured to select the minimum of the firstintermediate control variable and the second intermediate controlvariable as the control variable.
 4. The power delivery system of claim1, wherein the first physical quantity is associated with a constraintof the power source.
 5. The power delivery system of claim 4, whereinthe second physical quantity is associated with a constraint of thepower converter.
 6. The power delivery system of claim 1, wherein thesecond physical quantity is associated with a constraint of the powerconverter.
 7. A method comprising, in a power delivery system having apower converter configured to electrically couple to a power source andfurther configured to supply electrical energy to one or more loadselectrically coupled to an output of the power converter: generating,with a first control mechanism, a first intermediate control variablebased on a first physical quantity associated with the power deliverysystem; generating, with a second control mechanism, a secondintermediate control variable based on a second physical quantityassociated with the power delivery system; selecting a control variablefrom the first intermediate control variable and the second intermediatecontrol variable; controlling the power converter in accordance with acontrol variable; storing the control variable in a shared feedbackmemory element; and feeding back the control variable to inputs of thefirst control mechanism and the second control mechanism, such that: thefirst control mechanism generates the first intermediate controlvariable based on the first physical quantity and the control variable;and the second control mechanism generates the second intermediatecontrol variable based on the second physical quantity and the controlvariable.
 8. The method of claim 7, wherein the control variable is amaximum electrical current associated with the power delivery system. 9.The method of claim 8, wherein: the first intermediate control variableis a first electrical current variable; the second intermediate controlvariable is a second electrical current variable; and selecting thecontrol variable comprises selecting the minimum of the firstintermediate control variable and the second intermediate controlvariable as the control variable.
 10. The method of claim 7, wherein thefirst physical quantity is associated with a constraint of the powersource.
 11. The method of claim 10, wherein the second physical quantityis associated with a constraint of the power converter.
 12. The methodof claim 7, wherein the second physical quantity is associated with aconstraint of the power converter.
 13. A mobile device, comprising: apower source; one or more loads; a power converter electrically coupledto the power source and further configured to supply electrical energyto the one or more loads; and control circuitry configured to controlthe power converter in accordance with a control variable, comprising: afirst control mechanism configured to generate a first intermediatecontrol variable based on a first physical quantity associated with thepower delivery system; a second control mechanism configured to generatea second intermediate control variable based on a second physicalquantity associated with the power delivery system; a selectorconfigured to select the control variable from the first intermediatecontrol variable and the second intermediate control variable; and ashared feedback memory element configured to feed back the controlvariable to inputs of the first control mechanism and the second controlmechanism, such that: the first control mechanism generates the firstintermediate control variable based on the first physical quantity andthe control variable; and the second control mechanism generates thesecond intermediate control variable based on the second physicalquantity and the control variable.
 14. The mobile device of claim 13,wherein the control variable is a maximum electrical current associatedwith the power delivery system.
 15. The mobile device of claim 14,wherein: the first intermediate control variable is a first electricalcurrent variable; the second intermediate control variable is a secondelectrical current variable; and the selector is configured to selectthe minimum of the first intermediate control variable and the secondintermediate control variable as the control variable.
 16. The mobiledevice of claim 13, wherein the first physical quantity is associatedwith a constraint of the power source.
 17. The mobile device of claim16, wherein the second physical quantity is associated with a constraintof the power converter.
 18. The mobile device of claim 13, wherein thesecond physical quantity is associated with a constraint of the powerconverter.